1. Field of the Invention
The present invention relates to a control system for controlling an operating state of an internal combustion engine.
2. Description of Related Art
In known structure of an internal combustion engine of a vehicle, an air bypass passage is formed so that the air bypass passage bypasses a throttle valve disposed in an intake passage of the engine, and an air bypass valve is disposed in the air bypass passage for regulating a flow rate of air passing through the air bypass passage.
Usually, the above structure is used to stabilize an operating state of the internal combustion engine. A control system disclosed in Unexamined Japanese Patent Application Publication No. S54-159526 increases an opening degree of the air bypass valve when a load applied to the engine increases, for instance, when an air conditioner of a vehicle is operated. Thus, control for stabilizing the operating state of the engine is performed.
The above control system regulates the opening degree of the air bypass valve only for the purpose of stabilizing the operating state of the engine. However, in this case, there is a possibility that driving torque outputted from the engine to a drive shaft through a transmission is fluctuated by the regulation of the opening degree, and vibration of a vehicle body is increased by the fluctuation of the driving torque. The vibration of the vehicle body means vibration of a system (a vehicle body system, a sprung mass) mounted on a vibration system (an unsprung mass) such as driving wheels or driven wheels of the vehicle through suspension springs.